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The production of raw-crushed wind-turbine blade (RCWTB) and its addition to conventionally designed self-compacting Concrete (SCC) enable us to provide a second life to wind-turbine blades. However, SCC containing RCWTB must show proper fresh behavior, an aspect evaluated in this paper both experimentally and through simulations based on computational fluid dynamics (CFD) for RCWTB additions up to 3.0% by volume. In experimental terms, RCWTB reduced the flowability and passing ability of SCC, and slowed SCC flow, although the performance of SCC with 1.5% RCWTB was adequate under free-flow conditions. In terms of modeling, RCWTB did not impact yield stress and increased plastic viscosity. CFD modeling under free flow, regardless of the presence or not of obstacles simulating concrete reinforcement, was successful, especially in the long term. Nevertheless, the modeling of the passing ability was not accurate; precision could be improved by simulating the effect of the individual GFRP fibers within the SCC flow. Finally, the mechanical properties of SCC were negatively impacted by RCWTB, the stitching effect of the GFRP fibers not being effective in an SCC with a conventional design. A specific SCC design when adding RCWTB is therefore needed to advance in the use of this waste in this concrete type. [ABSTRACT FROM AUTHOR]

AbstractIn this research, masonry and concrete construction and demolition wastes (CDWs) were used as supplementary cementitious material (25% vol. residue of masonry, RM) and recycled coarse aggregate (RCA) in increasing levels (0%, 50% and 100% vol. residue of concrete), respectively, in the development of self-compacting concrete (SCC). The performance of SCC mixtures was evaluated in terms of fresh properties, compressive strength, resistance to both accelerated (1% CO2, 65% R.H. and 23 °C temperature) and natural carbonation as well as chloride penetration. Experimental results showed a monotonic workability reduction associated to the incorporation of increasing levels of RCA. In compressive strength, the SCC with RCA showed the greatest increase in this mechanical property after 28 days of accelerated exposure in the carbonation chamber, when compared to its water-cured counterpart. Yet, at 360 days of accelerated carbonation exposure, all SCCs showed compressive strength reductions compared to their water-cured counterparts. On the other hand, the chloride permeability resistance of the SCCs was low and very low at the ages evaluated. Thus, the findings of this study indicate that the use of CDW can generate SCCs with adequate fresh properties, compressive strength and carbonation and chloride penetration performance, which offers benefits for the environment. [ABSTRACT FROM AUTHOR]

Self-compacting concrete (SCC) is a specialized form of concrete known for its exceptional workability, high paste content, and incorporation of cement substitutes like silica fume, natural pozzolana, and slag. These cement alternatives offer various advantages including cost reduction, decreased carbon dioxide emissions, reduced depletion of natural resources, and enhanced properties in both fresh and hardened states. SCC finds application in diverse scenarios such as structures with densely packed reinforcement and tall shear walls, necessitating accurate performance prediction. This study aims to develop artificial neural network (ANN) models for forecasting the compressive strength, split tensile strength, and flexural strength of self-compacting concrete incorporating fly ash and waste copper slag, assessed at curing periods of 7, 28, 56, and 90 days. The ANN model comprises several input and output parameters, with model accuracy evaluated using Mean Squared Error (MSE) and R-squared (R2) metrics. Furthermore, the network's performance is evaluated through error histograms and regression network predictions using ANN. The Levenberg-Marquardt optimization method, implemented in MATLAB 2020a, is employed to effectively estimate the compression strength, split tensile strength, and flexural strength of self-compacting concrete, ensuring reliable results. [ABSTRACT FROM AUTHOR]

The present study aims to determine the mix proportion of binder, heavyweight aggregates, water-to-binder ratio, and additives to develop self-compacting concrete with a bulk density higher than 2600 kg m−3. It also aims to evaluate the engineering properties, pore structure, and microstructure of established heavyweight self-compacting concrete. Barite (BA), magnetite (MAG) or their mix (MIX) were used as fillers, while binder was composed of Portland cement, blast furnace slag, metakaolin, and limestone at a ratio of 65:15:5:15. Based on text results of V-funnel, S-Cone diameter and S-Cone time, the proportion mix and binder: filler: binder to cement ration was optimized as follows: 1) BA 1: 3.5: 0.42, 2) MAG 1: 4: 0.42, and 3) MIX 1: 3.75: 0.42 with maximal aggregate size not exceeding 2 mm. Not only the bulk density was influenced by aggregate, but also, the mechanical properties, shrinkage, dynamic modulus of elasticity pore structure, and microstructure were also found to be dependent on fillers. [ABSTRACT FROM AUTHOR]

The present study aims to investigate how the use of high‐range water reducer (HRWR) and variations in water/cement (W/C) ratio affect the properties of self‐consolidating concrete (SCC) while taking into account different proportions of polypropylene fibers (PF) and natural zeolite (NZ). A total of 28 samples were cast and analyzed. PF fractions ranging from 0% to 1.5% by weight were added, along with a substitution of 10% NZ for cement (50 kg/m3). Four W/C ratios (0.30, 0.35, 0.40, and 0.45) were tested, in addition to seven HRWR contents ranging from 5 to 6.5 kg/m3. Various tests were conducted to assess slump, T500, V‐funnel, L‐box, modulus of elasticity, and compressive, tensile, and flexural strengths. Novel models were developed to predict the properties of hardened concrete based on W/C, HRWR, PF, and NZ content. Findings indicated that optimal performance of PF‐reinforced SCC with NZ was achieved when up to 0.75% PF was combined with an HRWR content equivalent to 1.25% of the cement fraction and NZ ratio. Furthermore, the proposed models offer accurate predictions of both fresh and hardened‐state properties of PF‐reinforced SCC with NZ based on W/C and HRWR ratios. [ABSTRACT FROM AUTHOR]

Self-compacting concrete (SCC) is widely used in reinforced concrete buildings, owing to its ability to consolidate by weight and its lack of requirement for external vibration. Reinforced concrete buildings can be subjected to high strain rate loading during the early days of construction or in their service life. Thus, it is critical to understand the behaviour of concrete under high strain rate loadings at different ages. Minimal studies have previously focused on the early-age behaviour of concrete under high strain rates. This study tries to fill this gap. It focuses on the behaviour of M40 grade SCC under three levels of strain rate loading at ages of 1, 3, 7, 14 and 28 d. The split-Hopkinson pressure bar (SHPB) was used to test 45 SCC specimens of diameter 100 m and thickness 50 mm at high strain rates, ranging from 30 s−1 to 110 s−1, and the determined compressive strength, peak strain and elastic modulus results are compared with quasistatic test results of SCC specimens. The dynamic increase factor (DIF) determined in the SHPB experiment is compared with the CEB-fib code model. The results indicate that the DIF reduces as the concrete's strength and age increase. [ABSTRACT FROM AUTHOR]

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The development of self-compacting lightweight concretes is associated with solving two conflicting tasks: achieving a structure with both high flowability and homogeneity. This study aimed to identify the technological and rheological characteristics of the flow of concrete mixtures D1400...D1600 based on hollow microspheres in comparison with heavy fine-grained D2200 concrete and to establish their structural and physico-mechanical characteristics. The study of the concrete mixtures was carried out using the slump flow test and the rotational viscometry method. The physical and mechanical properties were studied using standard methods for determining average density and flexural and compressive strength. According to the results of the research conducted, differences in the flow behaviors of concrete mixtures on dense and hollow aggregates were found. Lightweight concretes on hollow microspheres exhibited better mobility than heavy concretes. It was shown that the self-compacting coefficients of the lightweight D1400...D1600 concrete mixtures were comparable with that of the heavy D2200 concrete. The rheological curves described by the Ostwald–de Waele equation showed a dilatant flow behavior of the D1400 concrete mixtures, regardless of the ratio of quartz powder to fractionated sand. For D1500 and D1600, the dilatant flow behavior changed to pseudoplastic, with a ratio of quartz powder to fractional sand of 25/75. The studied compositions of lightweight concrete can be described as homogeneous at any ratio of quartz powder to fractional sand. It was shown that concrete mixtures with a pronounced dilatant flow character had higher resistance to segregation. The value of the ratio of quartz powder to fractional sand had a statistically insignificant effect on the average density of the studied concretes. However, the flexural and compressive strengths varied significantly more in heavy concretes (up to 38%) than in lightweight concretes (up to 18%) when this factor was varied. The specific strength of lightweight and heavy concrete compositions with a ratio of quartz powder to fractional sand of 0/100 had close values in the range of 20.4...22.9 MPa, and increasing the share of quartz powder increased the difference between compositions of different densities. [ABSTRACT FROM AUTHOR]

Concrete is used worldwide as a construction material in many projects. It exhibits a brittle nature, and fibers' addition to it improves its mechanical properties. Polypropylene (PP) fibers stand out as widely employed fibers in concrete. However, conventional micro-PP fibers pose challenges due to their smooth texture, affecting bonding within concrete and their propensity to clump during mixing due to their thin and soft nature. Addressing these concerns, a novel type of PP fiber is proposed by gluing thin fibers jointly and incorporating surface indentations to enhance mechanical anchorage. This study investigates the incorporation of macro-PP fibers into high-strength concrete, examining its fresh and mechanical properties. Three different concrete strengths 40 MPa, 45 MPa, and 50 MPa, were studied with fiber content of 0–1.5% v/f. ASTM specifications were utilized to test the fresh and mechanical properties, while the RILEM specifications were adopted to test the bond of bar reinforcements in concrete. Test results indicate a decrease in workability, increased air content, and no substantial shift in fresh concrete density. Hardened concrete tests, adding macro-PP fibers, show a significant increase in splitting tensile strength, bond strength, and flexural strength with a maximum increase of 34.5%, 35%, and 100%, respectively. Concrete exhibits strain-hardening behavior with 1% and 1.5% fiber content, and the flexural toughness increases remarkably from 2.2 to 47.1. Thus, macro PP fibers can effectively improve concrete's mechanical properties and resistance against crack initiation and spread. [ABSTRACT FROM AUTHOR]

This study investigated the effects of using bagasse ash (BA) and metakaolin (MK) together as substitutes for cement in self-compacting concrete (SCC), together with the addition of glass fiber (GF), on the physical and mechanical characteristics of concrete. Eighteen SCC mixes were created, each containing different proportions of BA (0%, 10%, 15%, and 20%), MK (0%, 10%, 15%, and 20%), and BA and MK collectively (10% + 5% and 10% + 10%) as cement replacements with and without 0.1% GF. Using the results of the slump flow, T500 slump flow, V-funnel, and L-box tests, the performance of fresh SCC was determined. Furthermore, this study evaluated the strength, durability, and microstructural properties of the SCC samples. The SCC mix blended with 10% BA and 5% MK revealed better flowability as the slump flow increased from 692 mm to 715 mm. A strong linear correlation was discovered between the slump flow values (mm) and V-funnel duration (sec) and blocking ratio (H2 /H1 ) with R² = 0.8876 and R² = 0.8467, respectively. Of all test mixes, the SCC mix blended with 10% BA, 5% MK, and 0.1% GF (SCC1B10M5) demonstrated the highest degree of strength. At 56 days, the 10% BA, 5% MK, and 0.1 GF mix had 12.8%, 25.7%, and 22.2% higher compressive, flexural, and splitting tensile strengths than the control mix, respectively. SCC, combined with BA, MK, and GF, outperformed the control mix. After immersion in a 3% H2SO4 solution, the SCC mix having 10% BA, 5% MK, and 0.1% GF experienced a minimum reduction in weight loss and ultrasonic pulse velocity of 1.01% and 3.1%, respectively. Additionally, there was a decrease of 29.4% in the percentage of charges passed. The ideal composition was achieved by incorporating 10% BA, 5% MK, and 0.1% GF into the SCC mixture, resulting in a dense structure without any visible pores or cracks during the microstructural analysis. [ABSTRACT FROM AUTHOR]

In this paper, the possibility of utilising coarse recycled concrete aggregate (CRCA) obtained from a construction and demolition waste (CDW) plant in Delhi to make 60 MPa self-compacted concrete (SCC) was evaluated. The CRCA was used in as-collected condition and was not processed any further. The aggregate packing (bulk) density (APD) method was adopted to prepare the SCC-CRCA mixture in order to obtain an aggregate mixture exhibiting maximum bulk density/least void content (45%). In addition, SCC was made using aggregate mixtures in which the natural coarse aggregate (NCA) was replaced with CRCA at 0%, 20% and 100% of the total coarse aggregate content by weight. The cement, fly ash, silica fume and water were kept constant for all SCC mixtures. The effects of CRCA on the flow behaviour, mechanical strength, shrinkage characteristics and microstructure properties of SCC mixtures were evaluated. The test results indicated that SCC mixtures made with up to 45% CRCA replacement can be used for structural concrete, which is higher than that recommended in Indian (20%) and international specifications (35%) for traditionally vibrated (conventional) concrete. [ABSTRACT FROM AUTHOR]

Self-Compacting Concrete (SCC) has been widely utilized in construction projects and academic research due to its environmentally friendly components, such as fly ash and superplasticizers, which reduce water requirements. SCC's ability to self-deposit eliminates the need for vibration, resulting in cost and energy savings. However, some experts are hesitant about its broader application due to insufficient training in modern materials. Accurately assessing construction aggregates' compressive strength (CS) ensures structural safety. Soft computing methods, which offer a cost-effective and highly accurate alternative to experimental techniques, have attracted interest in modeling dependent variables. This paper presents a novel approach by combining a Support Vector Machine (SVM) with advanced optimization algorithms to estimate the CS of SCC mixtures accurately. The significance of this approach lies in the ability of the optimization algorithms to enhance the performance of the SVM, yielding more precise predictions and addressing the limitations of traditional methods. The developed models were evaluated using several performance metrics, with results showing a strong correlation between predicted and actual values, achieving an R² of 97.3%. Furthermore, the root mean square error (RMSE) was calculated at 3.81 MPa, demonstrating the effectiveness of the proposed method in predicting SCC's compressive strength with high accuracy. [ABSTRACT FROM AUTHOR]

Methods for the assessment of concrete pumpability are briefly reviewed; in particular, the rheology-based analytical model is introduced. With the application of different methods in representative cases of super high-rise building construction, the rheology-based model is validated. It is found that the rheology-based analytical model predicts the pumpability of modern high-flowability concrete with good accuracy. A series of parametric study is conducted to investigate the influence of important parameters concerned with concrete pumpability. The parameters having linear or nonlinear influence on pumpability are distinguished. This work provides valuable supports to the improvement of construction technology and project management of super high-rise buildings. [ABSTRACT FROM AUTHOR]

To protect the environment and reduce the consumption of natural resources, this study investigated the performance of self-compacting concrete (SCC) utilizing aeolian sand (AS) as a replacement for fine aggregate and recycled coarse aggregate (RCA) as a replacement for natural coarse aggregate. Twelve mixing ratios were prepared, with AS replacement ratios at 0, 20%, 40%, and 60% and RCA replacement ratios at 0, 25%, and 50%. The evaluation primarily focused on workability, uniaxial compressive strength, split tensile strength, stress–strain curve, modulus of elasticity, and axial compressive strength. The results indicated that both AS and RCA can enhance the performance of SCC at appropriate replacement ratios, and a 20% AS and 50% RCA replacement ratio significantly improved the performance of SCC. In addition, the effects of AS and RCA replacements on SCC were evaluated by several performance indexes, which provides a basis for subsequent experimental studies and demonstrates the feasibility of incorporating AS and RCA into SCC. [ABSTRACT FROM AUTHOR]

Abstract The cast in-situ pile is a widely used type of deep foundations which its execution in civil projects is increasing daily. The use of ordinary concrete in this type of piles causes technical and executive problems, a decrease in the compressive strength (CS) of concrete, and an increase in the permeability under the ground level. But use of the self-compacting concrete in the cast in-situ piles while increasing the CS of concrete ensures proper compaction, increase in the execution speed, and easy placing of concrete. In this article, utilizing the data obtained from the laboratory results and also the application of soft computing techniques, predicting the degree of CS of self-compacting concrete (SCC) in concrete piles was investigated. To estimate the CS of SCC, a total number of 7 inputs were implemented. Then, using gene expression programming (GEP) a model was presented for estimating the CS of SCC in the cast in-situ piles. The results of the neural network showed a precision of 99.98% which exhibits the high accuracy of the model. The use of this model could greatly help persons, companies, and research centers in the preparation and construction of self-compacting concrete with the desired CS.

Abstract Self-Compacting Concrete (SCC) allows for the use of non-desalted sea sand as a fine aggregate, but the durability of triple mix SCC with partial sea sand replacement remains unclear. To optimize binder and fine aggregate replacements, tests for consistency, setting times, soundness, compressive strength, and Ultrasonic Pulse Velocity were performed. Six SCC variations, incorporating 30 $$\%$$ % Class F Fly Ash (FA), 5 $$\%$$ % Ground Granulated Blast Furnace Slag (GGBS), and various fine aggregate combinations, were evaluated for their fresh, mechanical, microstructural, and durability properties. Results demonstrated that SCC with 50 $$\%$$ % sea sand and 50 $$\%$$ % manufactured sand achieved superior 90 $$^{th}$$ th day compressive strength. This improvement was attributed to accelerated cement setting and enhanced FA reactivity, leading to better hydration products. Microstructural analysis revealed more hydration products and fewer pores in specimens with 50 $$\%$$ % sea sand, due to the disconnected pore structure from Friedel’s salt formation. Chloride binding in concrete involves both chemical and physical mechanisms. Chemical binding is related to Friedel’s salt, while physical binding depends on Calcium-Silicate-Hydrate (C-S-H) content. Dense C-S-H formation from sea sand, confirmed by Scanning Electron Microscope (SEM) images, results in greater chloride binding. Additionally, aluminum oxide in FA and GGBS enhances chemical binding by forming Friedel’s salt.

Abstract Concrete is used worldwide as a construction material in many projects. It exhibits a brittle nature, and fibers' addition to it improves its mechanical properties. Polypropylene (PP) fibers stand out as widely employed fibers in concrete. However, conventional micro-PP fibers pose challenges due to their smooth texture, affecting bonding within concrete and their propensity to clump during mixing due to their thin and soft nature. Addressing these concerns, a novel type of PP fiber is proposed by gluing thin fibers jointly and incorporating surface indentations to enhance mechanical anchorage. This study investigates the incorporation of macro-PP fibers into high-strength concrete, examining its fresh and mechanical properties. Three different concrete strengths 40 MPa, 45 MPa, and 50 MPa, were studied with fiber content of 0–1.5% v/f. ASTM specifications were utilized to test the fresh and mechanical properties, while the RILEM specifications were adopted to test the bond of bar reinforcements in concrete. Test results indicate a decrease in workability, increased air content, and no substantial shift in fresh concrete density. Hardened concrete tests, adding macro-PP fibers, show a significant increase in splitting tensile strength, bond strength, and flexural strength with a maximum increase of 34.5%, 35%, and 100%, respectively. Concrete exhibits strain-hardening behavior with 1% and 1.5% fiber content, and the flexural toughness increases remarkably from 2.2 to 47.1. Thus, macro PP fibers can effectively improve concrete's mechanical properties and resistance against crack initiation and spread.

Abstract Self-compacting concrete (SCC) is an innovative material for construction that offers excellent workability and flowability while achieving effective and uniform compaction without the need for external vibration. Using an experimental approach, this study investigates the effect of incorporating arecanut fibers on the performance of self-compacting concrete (SCC). The focus is on optimizing the fiber content for improved concrete characteristics. The study examines three different fiber lengths (8 mm, 10 mm, and 12 mm) and three volume fractions (1%, 2%, and 3%) while partially replacing 30% of the cement by weight with fly ash. Tests on the workability of the SCC mixes revealed favorable characteristics: slump flow between 650 and 750 mm, T500 slump flow time of 2–5 s, V-funnel time of 5–10 s, L-box ratio of 0.8–1.0, and J-ring values within 0–10 mm as recommended by EFNARC guidelines. Furthermore, incorporating 30% fly ash and arecanut fibers significantly enhanced the hardened properties of the SCC, particularly its compressive strength. A concrete mix containing 2% of 10-mm long arecanut fibers achieved a compressive strength of 40.26 MPa, which is about 15.14% increase compared to the reference strength of 35 MPa. Similarly, using a 1% volume fraction of 12 mm arecanut fibers increased the split tensile strength by 14.04% and the flexural strength by 35.87% compared to the control mix. Fly ash and arecanut fibers enhance the durability of SCC by reducing Coulomb charges and improving resistance to chloride penetration. However, the increased water absorption rate of the fibers can lead to increased overall water absorption in the concrete. Microstructural analysis (SEM) revealed improved bonding and reduced voids, further supporting enhanced durability. Additionally, EDX analysis confirmed the presence of various elements from cement and fly ash, providing valuable data for evaluating the long-term performance of these SCC mixes.

Abstract The utilization of Self-compacting Concrete (SCC) has escalated worldwide due to its superior properties in comparison to normal concrete such as compaction without vibration, increased flowability and segregation resistance. Various other desirable properties like ductile behaviour, increased strain capacity and tensile strength etc. can be imparted to SCC by incorporation of fibres. Thus, this study presents a novel approach to predict 28-day compressive strength (C–S) of FR-SCC using Gene Expression Programming (GEP) and Multi Expression Programming (MEP) for fostering its widespread use in the industry. For this purpose, a dataset had been compiled from internationally published literature having six input parameters including water-to-cement ratio, silica fume, fine aggregate, coarse aggregate, fibre, and superplasticizer. The predictive abilities of developed algorithms were assessed using error metrices like mean absolute error (MAE), a20-index, and objective function (OF) etc. The comparison of MEP and GEP models indicated that GEP gave a simple equation having lesser errors than MEP. The OF value of GEP was 0.029 compared to 0.031 of MEP. Thus, sensitivity analysis was performed on GEP model. The models were also checked using some external validation checks which also verified that MEP and GEP equations can be used to forecast the strength of FR-SCC for practical uses.

Casting concrete underwater is concrete used for structural work underwater. The main problem in underwater casting is the separation of concrete constituent materials. Casting underwater also does not involve compaction. This study will examine the effect of peat water on the physical properties of underwater cast concrete. The additive used in this study is in liquid form, with a mixture of anti-washout material 1.8% and self-compacting concrete 5% to the weight of cement. The obtained slump flow value is 470 mm. The results of volume weight testing on variations of clean water mixtures immersed in clean water for seven days are 2248,14 kg/m3 and 2258,96 kg/m3 for 28 days, variations of clean water mixtures immersed in peat water for seven days are 2224,49 kg/m3 and 2219,39 kg/m3 for 28 days, and variations of peat water mixtures immersed in peat water for seven days are 2202,50 kg/m3 and 2191,08 kg/m3 for 28 days. The decrease in volume weight occurs in variations immersed in peat water. The results of porosity testing on 7-day and 28-day concrete age variations of peat water mixtures immersed in peat water are 9,94% and 10,78%, variations of clean water mixtures immersed in peat water are 9,84% and 10,28%, and variations of clean water mixtures immersed in clean water are 9,73% and 8,70%. The SEM test results show the surface shape of concrete using a magnification of 1000x, more pores on variations of peat water mixtures immersed in peat water, and variations of clean water mixtures immersed in peat water have uneven surfaces and pores. In contrast, variations of clean water mixtures immersed in clean water have better surfaces. The additive used can work well with peat water and clean water.

Self-compacting concrete (SCC) is an innovative material for construction that offers excellent workability and flowability while achieving effective and uniform compaction without the need for external vibration. Using an experimental approach, this study investigates the effect of incorporating arecanut fibers on the performance of self-compacting concrete (SCC). The focus is on optimizing the fiber content for improved concrete characteristics. The study examines three different fiber lengths (8 mm, 10 mm, and 12 mm) and three volume fractions (1%, 2%, and 3%) while partially replacing 30% of the cement by weight with fly ash. Tests on the workability of the SCC mixes revealed favorable characteristics: slump flow between 650 and 750 mm, T500 slump flow time of 2–5 s, V-funnel time of 5–10 s, L-box ratio of 0.8–1.0, and J-ring values within 0–10 mm as recommended by EFNARC guidelines. Furthermore, incorporating 30% fly ash and arecanut fibers significantly enhanced the hardened properties of the SCC, particularly its compressive strength. A concrete mix containing 2% of 10-mm long arecanut fibers achieved a compressive strength of 40.26 MPa, which is about 15.14% increase compared to the reference strength of 35 MPa. Similarly, using a 1% volume fraction of 12 mm arecanut fibers increased the split tensile strength by 14.04% and the flexural strength by 35.87% compared to the control mix. Fly ash and arecanut fibers enhance the durability of SCC by reducing Coulomb charges and improving resistance to chloride penetration. However, the increased water absorption rate of the fibers can lead to increased overall water absorption in the concrete. Microstructural analysis (SEM) revealed improved bonding and reduced voids, further supporting enhanced durability. Additionally, EDX analysis confirmed the presence of various elements from cement and fly ash, providing valuable data for evaluating the long-term performance of these SCC mixes. [ABSTRACT FROM AUTHOR]

This paper presents a study on the influence of the layered casting technology of self-compacting concrete (SCC) on the load-bearing capacity of interlayer bond in slab elements. The research was conducted on slab elements with dimensions of 750 × 750 × 150 mm, concreted from a single point of concrete delivery. The aim of this study was to analyse the influence of the height of the concreting top layer on the bond strength between the layers. The study utilised top layer heights of 50, 75, and 100 mm, which, according to the authors' experience, are the most common cases when making slab elements. The interlayer bond was determined by investigating the splitting tensile strength of cubic specimens cut from the concrete slabs. Computed tomography (CT) was employed to image the contact zone between the concrete layers. Based on the analysis of the CT imaging and the results of the strength tests, it was shown that the interlayer bond is influenced by both the height of the top layer and its free-spread distance from the casting point. A reduction in the interlayer bond strength was observed with decreasing the height of the top layer and increasing distance from the mixture supply point. The relationships obtained were linear and had a clearly negative slope. It was concluded that the valid recommendations and standards for the multilayer casting of SCC are too general. Therefore, we propose to detail the recommendations to reduce the risk of cold joints, which diminish the bond strength of the interlayer joints [ABSTRACT FROM AUTHOR]

In the present study, nylon waste fibers (NWF) were utilized for the first time to improve the impact resistance of self-compacting concrete (SCC) slabs against pistol shooting. Six ratios of NWF were used in the range of (0.25- 1.5 at an increment of 0.25) % with three different lengths (50, 70, and 90) mm for each ratio. The fresh properties, compressive strength, and Utara sonic pulse velocity (UPV) of SCC were also measured. The results indicate the positive role of NWF in improving compressive strength. However, the fresh properties are affected negatively by using NWF. The best impact resistance of the slab occurred when 1% of NWF with a length of 90 mm was utilized. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of element size on the microstructure of the steel–concrete interface in self-compacting concrete (SCC). Experiments were conducted on two types of test elements: a deep beam measuring 1440 × 640 × 160 mm and a wall element measuring 2240 × 1600 × 160 mm. The SCC mix was consistently pumped from the top, using a single casting point located near the formwork's edge. Horizontal steel ribbed rebars with a diameter of 16 mm were embedded in these elements. X-ray computed tomography (CT) was employed to provide three-dimensional insights into the microstructure of the rebar-to-concrete interface. An analysis of X-ray CT images from core samples revealed that the microstructure of this interface is influenced by the distance of the specimen from the mix casting point and its vertical position within the element. The combined effects of bleeding, air-pore entrapment, and plastic settlement within the SCI were observed under the top rebars. Their extent was independent of the type of element analyzed, suggesting that the deterioration of the SCI is related to the distance from the top surface of the element. These results elucidate phenomena occurring during the fresh state of concrete near reinforcing bars and their implications for bond properties. To date, some of the standards differentiate between bond conditions according to the depth of concrete beneath the rebar. In the view of the studies, this approach may be unduly rigorous. The findings offer valuable guidance for reinforced concrete execution and design. [ABSTRACT FROM AUTHOR]

The utilization of recycled materials in concrete technology has gained significant attention in recent years, promoting sustainability and resource conservation. This paper investigates the behavior of lightweight self-compacting concrete (LWSCC) with recycled tire steel fibers (RTSFs). The effects of RTSFs on the flowability of the composite material and its density were assessed. The mechanical properties of the developed material were examined and beam tests were performed, aiming to assess its feasibility for structural applications. The compressive and tensile strengths were determined to evaluate the mechanical properties of the developed concrete mixtures. The beam tests were conducted to assess the flexural behavior of the beam specimens. Three different steel fiber contents of 0, 0.5, and 1% volumetric fractions of concrete were used in this study. The test results indicate that incorporating the fibers did not negatively impact the flowability and density of the LWSCC mixtures. In addition, the use of RTSFs enhanced the tensile strength of the developed concrete mixtures, where fibrous concrete showed increases in the splitting tensile strength in the range of 38 to 76% over that of non-fibrous concrete. On the other hand, the compressive strength of the mixtures was not affected. The test beams with RTSFs exhibited improved flexural performance in terms of delaying and controlling cracking, enhancing ultimate load, and increasing ductility. Compared with the control non-fibrous beam, the increases in the cracking load, ultimate load, and ductility index were up to 63.8, 9.3, and 16%, respectively. The test results of the beams were compared with theoretical predictions, and good agreement was found. [ABSTRACT FROM AUTHOR]

This research examines the fresh properties, strength performance, and morphological analysis of self-compacting coconut shell concrete (SCCSC) blended with crushed coconut shell and manufactured sand (M-sand). Crushed coconut shell (CS) was used as a coarse aggregate (CA), and M-sand replaced river sand (R-sand) at 25%, 50%, 75%, and 100%. The study focused on the workability characteristics, mechanical behavior, and microstructural analysis of SCCSC. Experiments were performed on fresh and mechanical characteristics, including slump flow diameter, T500 slump flow time, L-Box blocking ratio, V-funnel and a wet sieving stability test. Mechanical characteristics include compressive, split tensile, flexural, impact resistance and bond strength. Utilizing M-sand develops the mechanical performance of SCCSC. The morphological characteristics, using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) and the X-ray diffraction (XRD) technique, were studied in this research work. The findings show that the addition of M-sand increases the concrete strength. The microstructural analysis demonstrates that adding different amounts of M-sand to SCCSC reduced the porosity and anhydrous cement percentage, although it increased calcium hydroxide and hydration products. The substitution of 100% M-sand at 28 days increased compressive strength by 3.79% relative to the reference SCCSC. Based on the findings, the mechanical strength of SCCSC containing M-sand significantly improved compared to the concrete with river sand. [ABSTRACT FROM AUTHOR]

This study investigates the application of artificial intelligence (AI) to predict the compressive strength of self-compacting concrete (SCC) through ultrasonic measurements, thereby contributing to sustainable construction practices. By leveraging advancements in computational techniques, specifically artificial neural networks (ANNs), we developed highly accurate predictive models to forecast the compressive strength of SCC based on ultrasonic pulse velocity (UPV) measurements. Our findings demonstrate a clear correlation between higher UPV readings and improved concrete quality, despite the general trend of decreased compressive strength with increased air-entraining admixture (AEA) concentrations. The ANN models show exceptional effectiveness in predicting compressive strength, with a correlation coefficient (R2) of 0.99 between predicted and actual values, providing a robust tool for optimizing SCC mix designs and ensuring quality control. This AI-driven approach enhances sustainability by improving material efficiency and significantly reducing the need for traditional destructive testing methods, thus offering a rapid, reliable, and non-destructive alternative for assessing concrete properties. [ABSTRACT FROM AUTHOR]

The utilization of Self-compacting Concrete (SCC) has escalated worldwide due to its superior properties in comparison to normal concrete such as compaction without vibration, increased flowability and segregation resistance. Various other desirable properties like ductile behaviour, increased strain capacity and tensile strength etc. can be imparted to SCC by incorporation of fibres. Thus, this study presents a novel approach to predict 28-day compressive strength (C–S) of FR-SCC using Gene Expression Programming (GEP) and Multi Expression Programming (MEP) for fostering its widespread use in the industry. For this purpose, a dataset had been compiled from internationally published literature having six input parameters including water-to-cement ratio, silica fume, fine aggregate, coarse aggregate, fibre, and superplasticizer. The predictive abilities of developed algorithms were assessed using error metrices like mean absolute error (MAE), a20-index, and objective function (OF) etc. The comparison of MEP and GEP models indicated that GEP gave a simple equation having lesser errors than MEP. The OF value of GEP was 0.029 compared to 0.031 of MEP. Thus, sensitivity analysis was performed on GEP model. The models were also checked using some external validation checks which also verified that MEP and GEP equations can be used to forecast the strength of FR-SCC for practical uses. [ABSTRACT FROM AUTHOR]

In order to study the change of mechanical properties and failure behavior of self-compacting concrete with different fly ash content, the FISH language in PFC2D and the linear bonding model built in the program were used to establish a single self-compacting concrete with different fly ash content. The discrete element model of the axial compression test was compared with the actual test results to analyze the internal failure form and force chain changes. The research shows that the ultimate strength of FA-SCC with different fly ash content increases first and then decreases, and the failure cracks are all diagonal cracks. The difference lies in the number of vertical cracks in the middle. The established two-dimensional discrete element numerical model type can well simulate the uniaxial compression test of fly ash self-compacting concrete structure, and can well observe the processcess of the generation of micro-cracks in the material, the expansion of cracks and the formation of diagonal penetration cracks when the axial compression failure occurs, which makes up for the indoor test only relying on the naked eye. At the same time, the axial compressive strength and stress-strain curves of the self-compacting concrete output by the model under different fly ash content are highly consistent with the laboratory test results, and the error of the maximum compressive strength measured does not exceed 7.1%, which is the result of fly ash. The discrete element simulation and mesostructure research of grey self-compacting concrete provide reference. [ABSTRACT FROM AUTHOR]

The objective of the current study is to evaluate the performance of Recycled Concrete Aggregates (RCA) based Self-compacting Concrete (RCA-SCC) comprising coal ashes and Silica Fume (SF). Coal ashes [Fly Ash (FA) and Coal Bottom Ash (CBA)] were incorporated as partial replacement for Ordinary Portland Cement (OPC) and Fine Natural Aggregates (FNA), respectively, while RCA were incorporated in place of Coarse Natural Aggregates (CNA). In order to compensate for the anticipated performance loss caused by the incorporation of RCA, a fixed percentage (10%) of SF was used as filler. The performance of aforesaid SCC was evaluated through various laboratory tests in fresh and hardened state. Five different substitution levels of CNA with RCA (0–100%), parallel with constant substitution level of FNA with CBA (10%) and OPC with SF + FA (10% + 20%) have been used throughout the investigation. Overall, the experimental outcomes along with regression results confirmed the potential of RCA-SCC prepared with CBA. RCA-SCC mix (25%) with coal ashes (FA + CBA) resulted in nearly equivalent performance to that of the reference SCC mix. Finally, the outcomes imply the successful contribution of SF, coal ashes (CBA + FA), and RCA leading towards the sustainable development of non-conventional SCC with identical performance. [ABSTRACT FROM AUTHOR]

In Algeria, glass waste is underutilized in the industrial sector; however, its potential use in civil engineering offers a significant ecological and economic opportunity. This approach could be a solution to eliminating illegal dumping sites, reduce pollution, and provide a new source of sustainable construction materials. In this context, this research aimed to produce self-compacting concrete (SCC) mixtures using recycled glass powder as a replacement for limestone filler. This research presents an experimental study investigating the impact of glass powder waste as a replacement for the traditionally used limestone filler in self-compacting concrete. To investigate the workability and compressive strength of the SCC studied, eleven concrete mixtures were prepared with varying substitution rates of limestone filler (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%) with powder glass. The use of powdered glass waste has beneficial effects, as the pozzolanic reaction generates an additional amount of hydrated calcium silicates. The results of the investigation showed an increase in compressive strength compared to the control concrete specimen (without glass powder). The best results were observed when incorporation ranged between 10% and 50%, with the optimal level being 30%, resulting in an 8.47% strength gain. This study contributes to the valorization of glass powder as a substitute for limestone filler. The results demonstrate positive effects on both fresh and hardened characteristics when using glass powder in proportions ranging from 10% to 50% of the filler mass. [ABSTRACT FROM AUTHOR]

This paper describes the research on micro-silica, popular in Kazakhstan ferrosilicon production technogenic waste, its impact on self-compacting concrete rheological and physical-engineering properties, and performance and durability improvement of building structures made of this concrete type utilizing volumetric fiber reinforcement. The paper includes the results of laboratory and industrial tests of self-compacting concrete mixtures (SCC) strength and operational properties. The most effective ratio of micro-silica as a filler in the binder and the optimal amount of low-modulus polypropylene fiber was selected to manufacture high-quality selfcompacting concrete of C25/30, C30/35, C35/40, C40/45 classes produced using local raw materials. Examples of compositions using micro-silica confirm the possibility of up to 20% cement consumption reduction and increase the concrete frost resistance to F340, reduction of self-compacting concrete volumetric water absorption by up to 30%, increase bending strength by up to 35% with the combined use of silica and polypropylene fiber in a right proportion are described here. The research results provide practical value for self-compacting and cast concrete Kazakhstani manufacturers. [ABSTRACT FROM AUTHOR]

Concrete is one of the most common construction materials used all over the word. In estimating the strength properties of concrete, laboratory works need to be carried out. However, researchers have adopted predictive models in order to minimize the rigorous laboratory works in estimating the compressive strength and other properties of concrete. Self-compacting concrete which is an advanced form of construction is adopted mainly in areas where vibrations may not be possible due to complexity of the form work or reinforcement. This work is targeted at predicting the compressive strength of self-compacting concrete using artificial intelligence techniques. A comparative performance analysis of all techniques is presented. The outcomes demonstrated that training in a Deep Neural Network model with several hidden layers could enhance the performance of the suggested model. The artificial neural network (ANN) model, possesses a high degree of steadiness when compared to experimental results of concrete compressive strength. ANN was observed to be a strong predictive tool, as such is recommended for formulation of many civil engineering properties that requires predictions. Much time and resources are saved with artificial intelligence models as it eliminates the need for experimental test which sometimes delay construction works. [ABSTRACT FROM AUTHOR]

Self-compacting concrete (SCC) is the most flowable concrete type that exerts high pressure on formwork. SCC is the most commonly used concrete globally for construction applications due to its cost-effectiveness. However, to make a formwork resist the exerted lateral pressure of SCC, it is required to have a suitable design for formwork. This paper presents a novel approach on how could create and prepare the Fiber Bragg Grating (FBG) optics using as a sensor to measure lateral pressure and temperature of SCC. To ensure the FBG sensor works properly a validated methodology is conducted. In the first stage, FBG sensors are calibrated with temperature sensitivity and then are calibrated with water pressure. The latter calibration is used to verify lateral pressure with SCC. However, this is not the only sensor used to record the result, a genuine sensor such as a transducer sensor has been positioned close to the FBG sensor to validate the results of the FBG sensor. The created FBG sensor demonstrates highly promising results, effectively validating the outcomes of the transducer sensor, while also reducing costs and enhancing usability for construction applications. [ABSTRACT FROM AUTHOR]

AbstractThe concrete equivalent mortar (CEM) method, mainly used in the laboratory, offers a course that facilitates and accelerates experimental test programs with relatively small amounts of materials. To this end, two CEM mixes, with natural and recycled aggregates, at different superplasticizer (SP) concentrations, were tested. The key objective was to investigate how CEM flow property changed at 0, 30, and 60 min of resting time, emphasizing the material’s structuring and destructuring effects. This study describes the flow behaviour of CEMs applying specific tools. Also, a vane-geometry rheometer was used to obtain rheological flow curves. Whatever the SP content in the structuring state, the results indicated reduced flow properties over time. However, an SP content of 1.3% retard the structural build-up property that was not evident at 60 min-rest time. Spread diameters ranging between 300 and 400 mm are measured with the mini cone immediately after mixing. After 60 min of resting time, these diameters were reduced between 260 and 300 mm. Remixing after prolonged rest periods reduces the flow stress values, which decrease from 10 to 18 Pa to 6 to 14 Pa. After a structural build-up at a rest time, the structural break-down effect by remixing re-fluidifies the mixtures. The fluidity has recovered its initial state, reflecting a thixotropic property. [ABSTRACT FROM AUTHOR]

Improvement of hydrophysical properties and corrosion resistance of self-compacting concrete to the effects of alternate freezing–thawing and aggressive soils of Southern and Central Kazakhstan is of interest to a wide range of researchers from the side of practical application of the obtained results in construction practice. It is proposed to form a spatially reinforced fine crystalline structure of a cement matrix with the maximum dense packing by using a complex modifier (hyperplasticizer + polymer + microsilica + fibro fibers) in the composition of self-compacting concretes (SCCs). The introduction of the calculated amount of the above additives increases the operational reliability of the current SCC compositions, increasing the water resistance to W16, frost resistance to F = 500, increasing the compressive strength by 20%, and reducing the mass loss of samples during corrosion leaching to 50%. It has been experimentally established that the proposed addition of the complex modifier (hyperplasticizer + polymer + microsilica + fibro fibers) to the SCC composition allows obtaining self-compacting concrete of high quality with improved performance characteristics (compressive strength, water resistance, frost resistance, and corrosion resistance). Studies have shown that the complex modifier-modified SCC compositions have a high degree of resistance in aggressive environments and leaching corrosion. Based on the results of the conducted tests, it is possible to recommend the obtained SCC compositions for the production of building products working in the zone of alternating freezing–thawing and aggressive soils. [ABSTRACT FROM AUTHOR]

Through the optimized design of the mix proportion of self-compacting concrete for steel-shell immersed tube of Shenzhen -Zhongshan Link, the effects of expansive agent and super absorbent resin on the working performance and compressive strength of self-compacting concrete were discussed, and their effects on the early shrinkage and long -term shrinkage deformation were emphatically studied. The results show that adding appropriate amount of expansive agent and super absorbent resin can improve the working performance of self-compacting concrete, but it began to have an adverse effect on the workability and the strength when the addition amount continued to increase. Compared with expansive agent, adding super absorbent resin can more effectively improve the volume stability of self-compacting concrete. [ABSTRACT FROM AUTHOR]

A sustainable and green approach to concrete mix design is fundamental for the construction sector in terms of reducing carbon dioxide ( CO 2 ) emissions and conserving non-renewable natural resources. This article proposes a novel mix design method for sustainable high-strength self-compacting concrete (HSSCC) based on rheological and mechanical properties with the aim of reducing cement content in such mixes. HSSCC mixes were designed using ground granulated blast furnace slag (GGBS) and fly ash to replace up to 40% of the cement content and tested for target compressive strengths ranging between 70 and 100 MPa. The proposed design method was numerically programmed to provide straightforward and realistic guidance in the form of design charts and verified through the design and production of sixteen HSSCC mixes consisting of varying sand-to-aggregate ratios (S/A). All mixes satisfied the self-compacting concrete criteria in the fresh state and achieved the targeted viscosity and compressive strength values. The effects of S/A and paste-to-solid (P/S) ratios on the rheological properties were evaluated. The experimental results demonstrated that the proposed mix design method could produce HSSCC with excellent fresh and mechanical characteristics while being eco-efficient with respect to CO 2 emissions and cement consumption. [ABSTRACT FROM AUTHOR]

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Currently, in Vietnam, the natural sand resource is depleted; thus, it is unable to meet the growing demand for construction. In this context, recycled fine aggregate (RFA) from waste concrete emerges as an effective alternative for sand in the production of self-compacting concrete (SCC). In this paper, the author presents the experimental results on the properties of SCC with high fly ash content using RFA. The research utilizes RFA to replace natural sand at the rates of 0% and 100%, respectively while applying fly ash concurrently at a 50% volume ratio of cement. The evaluated properties of the SCC include its workability, compressive strength, flexural tensile strength, chloride ion permeability, and water absorption. The research results show that the use of RFA combined with high fly ash content can produce SCC that meets EFNARC requirements, with only a 1.48% reduction in compressive strength, 1.85% decrease in flexural tensile strength, 19.79% reduction in chloride ion permeability, and 5.12% increase in water absorption compared to the use of natural sand. These findings demonstrate the effectiveness of incorporating RFA and high fly ash to replace natural sand and cement in SCC production, opening up prospects in the construction industry with positive environmental impacts. [ABSTRACT FROM AUTHOR]

Workers in the construction industry must endure different weather conditions, long working hours, and engage in repetitive and strenuous jobs with unrealistic deadlines. Sick leaves, caused by accidents and by work-related diseases, are common in the construction industry. Hand–arm vibration from hand-held power tools is a cause of significant ill health (disorders of the blood vessels, nerves, and joints). Self-compacting concrete (SCC) is a fluid concrete and does not need to be vibrated. Despite the health advantages of SCC, its market share in Sweden is lower than in comparable countries. The aim of this article is to describe views, opinions, and knowledge concerning the work environment and health in concrete casting and to identify barriers and facilitators of SCC usage. Semi-structured interviews were conducted with 24 interviewees from the construction industry in Sweden. The answers were analysed from a human–technology–organisation (HTO) perspective in order to identify barriers and facilitators for a broader usage of SCC. The results indicate that knowledge about SCC is low within the Swedish construction industry, including educational institutions; when SCC is chosen, it is chosen exclusively due to its technical characteristics, and not because it eliminates vibrations. Barriers to a broader usage of SCC comprise an incomplete knowledge base, clients who never choose it, recipes that are said to be too demanding, and workplace traditions. Facilitators comprise large companies investing in knowledge development about SCC and engaged persons promoting it. This study used an HTO-based model (BTOH) to identify barriers and facilitators for a broader usage of SCC, thus contributing to a deeper understanding of reasons for the low usage of SCC and ways of increasing it. [ABSTRACT FROM AUTHOR]

Abstract This work studies the feasibility of using rice husk ash (RHA) as a partial replacement for Brazilian Portland cement in producing self-compacting concrete for structural purposes. The RHA used is produced under controlled burning conditions in a fluidized bed. The concrete mix design is presented in detail to show how to find the best combination of the regional material to produce self-compacting concretes with good fresh and hardened characteristics. Concretes produced in the proportions of 5%, 10%, 15%, 20%, and 25% of replacement of cement by RHA have been studied, with the addition of 15% of fly ash and w/b of 0.45. In the fresh state, flowability, viscosity, and passing ability tests have been conducted. Additionally, mechanical tests were performed to assess the axial compressive strength and splitting tensile strength in the hardened state. The fresh state properties are influenced by the RHA content, reducing its flowability and passing ability with the increase of this material. The hardened state properties of the mixtures with RHA have shown increased resistance when compared to plain concrete. The mixture with 15% replacement had the best results. Concretes of 20% and 25% had their strength increased to a lesser degree. However, they remain a good option when increasing the superplasticizer quantity to improve the fluid state's properties.

Self-compacting concrete is regarded as one of the newest types of concrete due to its durability, efficiency, viscosity, stability, flowability, and resistance. Today, one of the most pressing environmental challenges is the disposal of solid waste, and one of the plastic materials discarded as waste after use is plastic packaging belts. These are made on the basis of polypropylene, as well as the factory Iron smelting mines are the main source of iron oxide waste production. Studies using recycled plastic fibers (30 mm × 0.3 mm) and waste iron oxide as cost-effective additives in self-compacting concrete (SCC) are presented. The effects on fresh and hardened properties were evaluated at various additive contents. Fresh and hardened properties of self-compacting concrete (SCC) were evaluated with and without fiber and iron oxide additives. Tests included workability (slump flow, funnel), strength (compressive, tensile), and durability (ultrasonic pulse speed, permeability). Experiments revealed that increasing the amount of recycled plastic fibers and waste iron oxide in self-compacting concrete (SCC) led to higher compressive and tensile strengths at both 7 and 28 days. These strength increases ranged from 2 to 9.68 MPa for compressive strength and 1.61–7.44 MPa for tensile strength, compared to the control specimen without additives.